The following generally relates to electric power distribution system feeder automation, and more particularly relates to soft PLC technology-based feeder automation logic development and implementation.
Electric utilities often rely on a trouble call system where customers can report outages to the utility. More specifically, when a fault occurs and customers experience a power outage, a customer(s) may call the utility and report the power outage. After receiving the power outage report, the utility may send a crew to the field to investigate the fault location and figure out and implement a switching scheme to first isolate the fault and then restore service to as many impacted customers as possible while the faulty feeder part is being repaired.
By using feeder automation logic, the crew no longer has to be sent out to troubleshoot the fault. Feeder automation logic automatically alters the topological structure of feeder systems by changing the open/close status of switches under abnormal operating conditions. In particular, when a fault occurs, feeder automation logic automatically selectively changes switch states to isolate a fault and restore power to as much load as possible. Feeder automation logic can reduce the power outage duration relative to sending out a crew to troubleshoot a fault and improve the distribution system reliability level.
When used in connection with network communication and distributed control, feeder automation at the network level is enabled. That is, the feeder system operating condition can be monitored and controlled by a feeder automation controller and multiple intelligent electronic devices (IED) that are equipped with switches in the feeder network. The IEDs send system information to the controller and in response the controller executes the feeder automation logic that identifies a fault and the location of the fault and fault isolation and power restoration solutions. The fault isolation and power restoration control commands are then sent to the IEDs, which implement the switch status change accordingly.
Feeder automation logic can be implemented in either a centralized or a distributed scheme. The centralized feeder automation scheme includes master controllers located in substations and IEDs associated with switches in the feeder network. The master controllers communicate with the IEDs in a master-to-slave mode. The master controller can be either a high-end industrial computer or a low-end programmable logic controller (PLC) or IEDs. In the distributed feeder automation scheme, each IED associated with a switch in the feeder network may work as a local feeder automation controller that communicates with other IEDs in a peer-to-peer mode to collect the network information and execute the feeder automation algorithms. The IEDs are used as local controllers.
High-end industrial computers enable the use of an advanced, high-end programming environments and languages (such as Visual Studio, C#, C++, etc.) to implement complex feeder automation logic. As a result, the development of feeder automation logic is efficient and the developed logic can provide end users (e.g., general field electrical engineers) with user-friendly interfaces. More recently, soft PLC technology has been used in electric power applications. Soft PLC is software that allows users to build PLC programs on standard computers. Soft PLC software runs on an ordinary computer and mimics the operation of a standard PLC and supports the IEC 61131-3 standard. The soft PLC programs can be downloaded to both PLCs and IEDs.
Unfortunately, some field engineers may not be able to easily understand or customize feeder automation logic that is developed based on the advanced, high-end programming environments and languages (such as Visual Studio, C#, C++, etc.). Such engineers often prefer to use low-end programming tools, controllers such as PLCs or, and the IEC 61131-3 standard PLC programming languages such as ladder diagram (LD), function block diagram (FBD), sequential function chart (SFC), structured text (ST), and instruction list (IL) as they can easily understand and customize the feeder automation logic. Unfortunately, logic developed using low-end tools generally require a high degree of effort and developers often have to build the logic from scratch. Moreover, the resulting feeder automation logic often is dependent on proprietary PLC hardware specifications and cannot be generalized.